maint: Use C++11 nullptr rather than 0 or NULL when possible. * FigureWindow.h, Logger.cc, Menu.cc, MouseModeActionGroup.h, Object.h, ObjectFactory.cc, ObjectProxy.h, color-picker.h, documentation-dock-widget.h, files-dock-widget.h, find-files-dialog.h, history-dock-widget.h, file-editor-tab.cc, file-editor.cc, file-editor.h, find-dialog.h, main-window.cc, main-window.h, octave-dock-widget.h, parser.cc, parser.h, webinfo.h, resource-manager.cc, shortcut-manager.cc, shortcut-manager.h, terminal-dock-widget.h, welcome-wizard.cc, welcome-wizard.h, workspace-model.h, workspace-view.h, __magick_read__.cc, call-stack.cc, call-stack.h, cdisplay.c, display.cc, dlmread.cc, dynamic-ld.cc, ft-text-renderer.cc, gl2ps-print.cc, graphics.cc, graphics.in.h, input.h, interpreter.cc, interpreter.h, ls-hdf5.cc, mex.cc, mxarray.in.h, oct-errno.in.cc, oct-fstrm.cc, oct-iostrm.h, oct-procbuf.cc, oct-stdstrm.h, oct-stream.cc, oct-stream.h, octave-link.cc, pager.cc, pr-output.cc, profiler.h, qz.cc, sighandlers.cc, strfns.cc, symtab.cc, symtab.h, typecast.cc, urlwrite.cc, variables.cc, __eigs__.cc, __init_fltk__.cc, __ode15__.cc, colamd.cc, ov-base-int.cc, ov-base.cc, ov-bool-mat.cc, ov-bool-sparse.cc, ov-builtin.cc, ov-class.cc, ov-classdef.cc, ov-complex.cc, ov-cx-diag.cc, ov-cx-mat.cc, ov-cx-sparse.cc, ov-fcn-handle.cc, ov-fcn-inline.cc, ov-flt-complex.cc, ov-flt-cx-diag.cc, ov-flt-cx-mat.cc, ov-flt-re-diag.cc, ov-flt-re-mat.cc, ov-java.cc, ov-java.h, ov-lazy-idx.cc, ov-perm.cc, ov-range.cc, ov-re-diag.cc, ov-re-mat.cc, ov-re-sparse.cc, ov-str-mat.cc, ov-struct.cc, ov-usr-fcn.h, octave.cc, octave.h, bp-table.cc, jit-ir.cc, jit-ir.h, jit-typeinfo.cc, jit-typeinfo.h, lex.h, pt-arg-list.cc, pt-arg-list.h, pt-array-list.h, pt-cell.h, pt-classdef.h, pt-colon.cc, pt-decl.h, pt-eval.cc, pt-eval.h, pt-except.h, pt-idx.h, pt-jit.cc, pt-jit.h, pt-loop.h, pt-mat.h, pt-select.h, pt.h, CSparse.cc, dSparse.cc, DASPK.cc, DASRT.cc, DASSL.cc, oct-fftw.cc, oct-rand.cc, oct-spparms.cc, child-list.cc, file-ops.cc, mach-info.cc, oct-env.cc, oct-time.cc, cmd-edit.cc, cmd-hist.cc, oct-locbuf.cc, oct-shlib.cc, pathsearch.cc, singleton-cleanup.cc, unwind-prot.h, url-transfer.cc: Use C++11 nullptr rather than 0 or NULL when possible.

--- a/libgui/graphics/Object.h	Fri Apr 28 15:29:39 2017 -0400
+++ b/libgui/graphics/Object.h	Fri Apr 28 13:19:12 2017 -0700
@@ -42,7 +42,7 @@
     Q_OBJECT
 
   public:
-    Object (const graphics_object& go, QObject *obj = 0);
+    Object (const graphics_object& go, QObject *obj = nullptr);
 
     virtual ~Object (void);
 
@@ -83,7 +83,7 @@
     void slotRedraw (void);
     void slotPrint (const QString& file_cmd, const QString& term);
 
-    void objectDestroyed (QObject *obj = 0);
+    void objectDestroyed (QObject *obj = nullptr);
 
   protected:
     static Object * parentObject (const graphics_object& go);